Flexible display apparatus

ABSTRACT

A flexible display apparatus including a bending area and a non-bending area. The flexible display apparatus further includes a display panel and a polarizing structure disposed on the display panel. The polarizing structure includes a λ/4 phase retardation layer, a linear polarizer disposed on the λ/4 phase retardation layer, and a first adhesive structure disposed between the λ/4 phase retardation layer and the linear polarizer. The linear polarizer includes a stretched polymer film. The first adhesive structure is an adhesive layer with a glass transition temperature that is greater than or equal to 40° C. and less than or equal to 150° C. Accordingly, deformation of the λ/4 phase retardation layer may be prevented or reduced when the flexible display apparatus is folded or bent, thereby improving display quality.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.17/682,636, filed on Feb. 28, 2022, which is a Continuation of U.S.patent application Ser. No. 16/552,725, filed on Aug. 27, 2019, issuedas U.S. Pat. No. 11,262,613, which is a Continuation of U.S. patentapplication Ser. No. 15/646,044, filed Jul. 10, 2017, which claimspriority to and the benefit of Korean Patent Application No.10-2016-0159639, filed Nov. 28, 2016, each of which is incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND

Exemplary embodiments relate to a display apparatus including apolarizing member. More particularly, exemplary embodiments relate to aflexible display apparatus including a polarizing member, thedeformation of which is minimized (or at least reduced) when theflexible display apparatus is bent, folded, twisted, or otherwisedeformed.

DISCUSSION

Various display apparatuses are being developed that can be used formultimedia devices, such as televisions, mobile phones, notebookcomputers, tablets, navigation devices, game machines, and the like.Further effort has been devoted to the development of flexible displayapparatuses that are capable of having their shape variously changed,such as through being bent, being folded, being twisted, or otherwisebeing deformed. When the shape of such a flexible display apparatus ischanged, stress is applied to various members constituting the displayapparatus, and, as such, deformation of the various members of thedisplay apparatus may occur. This deformation may cause, at least inpart, issues that degrade display quality.

The above information disclosed in this section is only for enhancementof an understanding of the background of the inventive concepts, and,therefore, it may contain information that does not form prior artalready known to a person of ordinary skill in the art.

SUMMARY

One or more exemplary embodiments provide a flexible display apparatusthat is capable of improving display quality by providing an adhesivemember having a high glass transition temperature between opticalfunctional layers included in a polarizing member so as to minimize (orat least reduce) deformation of the polarizing member resulting fromvarious usage forms of the flexible display apparatus.

Additional aspects will be set forth in the detailed description whichfollows, and, in part, will be apparent from the disclosure, or may belearned by practice of the inventive concepts.

According to one or more exemplary embodiments, a flexible displayapparatus includes a bending area and a non-bending area. The flexibledisplay apparatus further includes a display panel and a polarizingstructure disposed on the display panel. The polarizing structureincludes a λ/4 phase retardation layer, a linear polarizer disposed onthe λ/4 phase retardation layer, and a first adhesive structure disposedbetween the λ/4 phase retardation layer and the linear polarizer. Thelinear polarizer includes a stretched polymer film. The first adhesivestructure is an adhesive layer with a glass transition temperature thatis greater than or equal to 40° C. and less than or equal to 150° C.Accordingly, deformation of the λ/4 phase retardation layer may beprevented or reduced when the flexible display apparatus is folded orbent, thereby improving display quality.

According to one or more exemplary embodiments, a flexible displayapparatus includes a display panel and a polarizing structure disposedon the display panel. The display panel includes a bending area that istransformable into a bent shape or has a bent shape with respect to abending axis extending in one direction. The polarizing structureincludes: a λ/4 phase retardation layer including a liquid crystalcoating layer; a first adhesive structure disposed on the λ/4 phaseretardation layer, the first adhesive structure being an adhesive layerwith a glass transition temperature that is greater than or equal to 40°C. and less than or equal to 150° C.; and a linear polarizer disposed onthe first adhesive structure, the linear polarizer including a stretchedpolymer film. Accordingly, deformation of the λ/4 phase retardationlayer may be prevented or reduced when the flexible display apparatus isfolded or bent, thereby improving display quality.

The foregoing general description and the following detailed descriptionare exemplary and explanatory and are intended to provide furtherexplanation of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the inventive concepts, and are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments of the inventive concepts, and, together with thedescription, serve to explain principles of the inventive concepts.

FIG. 1A is a perspective view illustrating a flexible display apparatusin an unbent state according to one or more exemplary embodiments.

FIG. 1B is a cross-sectional view of the flexible display device of FIG.1A taken along sectional line I-I′ according to one or more exemplaryembodiments.

FIG. 2A is a perspective view illustrating the flexible displayapparatus of FIG. 1A in a first bent state according to one or moreexemplary embodiments.

FIG. 2B is a cross-sectional view of the flexible display apparatus ofFIG. 2A taken along sectional line II-IP according to one or moreexemplary embodiments.

FIG. 3A is a perspective view illustrating the flexible displayapparatus of FIG. 1A in a second bent state according to one or moreexemplary embodiments.

FIG. 3B is a cross-sectional view of the flexible display device of FIG.3A taken along sectional line III-III′ according to one or moreexemplary embodiments.

FIG. 4A is a perspective view illustrating a flexible display apparatusaccording to one or more exemplary embodiments.

FIG. 4B is a cross-sectional view of the flexible display apparatus ofFIG. 4A taken along sectional line IV-IV′ according to one or moreexemplary embodiments.

FIG. 5 is a cross-sectional view illustrating a flexible displayapparatus according to one or more exemplary embodiments.

FIG. 6 is a cross-sectional view illustrating a polarizing member of aflexible display apparatus according to one or more exemplaryembodiments.

FIGS. 7A, 7B, 7C, and 8 are cross-sectional views illustratingpolarizing members of flexible display apparatuses according to variousexemplary embodiments.

FIG. 9 illustrates a relationship between optical axes of opticalmembers included in a polarizing member according to one or moreexemplary embodiments.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments. It is apparent, however,that various exemplary embodiments may be practiced without thesespecific details or with one or more equivalent arrangements. In otherinstances, well-known structures and devices are shown in block diagramform in order to avoid unnecessarily obscuring various exemplaryembodiments.

Unless otherwise specified, the illustrated exemplary embodiments are tobe understood as providing exemplary features of varying detail ofvarious exemplary embodiments. Therefore, unless otherwise specified,the features, components, modules, layers, films, panels, regions,aspects, etc. (hereinafter collectively referred to as “elements”), ofthe various illustrations may be otherwise combined, separated,interchanged, and/or rearranged without departing from the disclosedexemplary embodiments. Further, in the accompanying figures, the sizeand relative sizes of elements may be exaggerated for clarity and/ordescriptive purposes. When an exemplary embodiment may be implementeddifferently, a specific process order may be performed differently fromthe described order. For example, two consecutively described processesmay be performed substantially at the same time or performed in an orderopposite to the described order. Also, like reference numerals denotelike elements.

When an element is referred to as being “on,” “connected to,” or“coupled to” another element, it may be directly on, connected to, orcoupled to the other element or intervening elements may be present.When, however, an element is referred to as being “directly on,”“directly connected to,” or “directly coupled to” another element, thereare no intervening elements present. Further, the DR1-axis, theDR2-axis, and the DR3-axis are not limited to three axes of arectangular coordinate system, and may be interpreted in a broadersense. For example, the DR1-axis, the DR2-axis, and the DR3-axis may beperpendicular to one another, or may represent different directions thatare not perpendicular to one another. For the purposes of thisdisclosure, “at least one of X, Y, and Z” and “at least one selectedfrom the group consisting of X, Y, and Z” may be construed as X only, Yonly, Z only, or any combination of two or more of X, Y, and Z, such as,for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items.

Although the terms “first,” “second,” etc. may be used herein todescribe various elements, these elements should not be limited by theseterms. These terms are used to distinguish one element from anotherelement. Thus, a first element discussed below could be termed a secondelement without departing from the teachings of the present disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,”“above,” “upper,” “over,” and the like, may be used herein fordescriptive purposes, and, thereby, to describe one element'srelationship to another element(s) as illustrated in the drawings.Spatially relative terms are intended to encompass differentorientations of an apparatus in use, operation, and/or manufacture inaddition to the orientation depicted in the drawings. For example, ifthe apparatus in the drawings is turned over, elements described as“below” or “beneath” other elements or features would then be oriented“above” the other elements or features. Thus, the exemplary term “below”can encompass both an orientation of above and below. Furthermore, theapparatus may be otherwise oriented (e.g., rotated 90 degrees or atother orientations), and, as such, the spatially relative descriptorsused herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof. It is also noted that, as used herein, the terms“substantially,” “about,” and other similar terms, are used as terms ofapproximation and not as terms of degree, and, as such, are utilized toaccount for inherent deviations in measured, calculated, and/or providedvalues that would be recognized by one of ordinary skill in the art.

Various exemplary embodiments are described herein with reference tosectional and/or exploded illustrations that are schematic illustrationsof idealized exemplary embodiments and/or intermediate structures. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should not beconstrued as limited to the particular illustrated shapes of regions,but are to include deviations in shapes that result from, for instance,manufacturing. In this manner, regions illustrated in the drawings areschematic in nature and shapes of these regions may not illustrate theactual shapes of regions of a device, and, as such, are not intended tobe limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and will not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

FIG. 1A is a perspective view illustrating a flexible display apparatusin an unbent state according to one or more exemplary embodiments. FIG.1B is a cross-sectional view of the flexible display device of FIG. 1Ataken along sectional line I-I′ according to one or more exemplaryembodiments. FIG. 2A is a perspective view illustrating the flexibledisplay apparatus of FIG. 1A in a first bent state according to one ormore exemplary embodiments. FIG. 2B is a cross-sectional view of theflexible display apparatus of FIG. 2A taken along sectional line II-IPaccording to one or more exemplary embodiments. FIG. 3A is a perspectiveview illustrating the flexible display apparatus of FIG. 1A in a secondbent state according to one or more exemplary embodiments. FIG. 3B is across-sectional view of the flexible display device of FIG. 3A takenalong sectional line III-III′ according to one or more exemplaryembodiments.

FIGS. 1A, 1B, 2A, 2B, 3A, and 3B illustrate a foldable display apparatusas an example of a flexible display apparatus DD; however, exemplaryembodiments are not limited thereto or thereby. For instance, theflexible display apparatus DD may include a display apparatus with aportion that is bent by a tensile force, a compressive force, atorsional force, and/or the like.

Referring to FIG. 1A, a display surface IS of the flexible displayapparatus DD on which an image IM is displayed is parallel to a planedefined by a first direction DR1 and a second direction DR2. A directionnormal to the display surface IS that defines a thickness direction ofthe flexible display apparatus DD is indicated by a third direction DR3.The front (or the upper surface) and the rear (or the lower surface) ofeach member are distinguished by the third direction DR3. It is noted,however, that the directions indicated by the first, second, and thirddirections DR1, DR2, and DR3 are relative concepts, and may be convertedto other directions. Hereinafter, first to third directions will beindicated by and referred to as the first to third directions DR1, DR2,and DR3 respectively.

The flexible display apparatus DD may include a plurality of areasdefined according to a form of operation of the flexible displayapparatus DD. The flexible display apparatus DD may include a bendingarea BA, which may be bent with respect to a bending axis BX (see, e.g.,FIG. 2A), and a non-bending area NBA, which may not be bent. Theflexible display apparatus DD may include at least one bending area BAand at least one non-bending area NBA. As seen in FIG. 1A, the flexibledisplay apparatus DD includes one bending area BA and two non-bendingareas NBA, but exemplary embodiments are not limited thereto or thereby.For example, the flexible display apparatus DD may include a pluralityof bending areas BA. It is also contemplated that the flexible displayapparatus DD may include more one or more (e.g., more than two)non-bending areas NBA. The bending area BA and the non-bending area NBAmay be disposed to be coupled together in the flexible display apparatusDD. For example, non-bending areas NBA may be disposed on opposing sidesof the bending area BA.

The display surface IS of the flexible display apparatus DD may includea plurality of areas. The flexible display apparatus DD may include adisplay area DD-DA in which the image IM is displayed, and a non-displayarea DD-NDA adjacent to the display area DD-DA. The non-display areaDD-NDA is an area in which the image IM is not displayed. In FIG. 1A,application icons and a clock window are illustrated as an example ofthe image IM. The display area DD-DA may be a quadrangular shape. Thenon-display area DD-NDA may be disposed to enclose the display areaDD-DA. It is noted, however, that exemplary embodiments are not limitedthereto or thereby, and the shape of the display area DD-DA and theshape of the non-display area DD-NDA may be relationally designed in anysuitable manner.

Referring to FIG. 1B, the flexible display apparatus DD may include adisplay panel DP, and a polarizing member (or structure) PM disposed onthe display panel DP. Additionally, the flexible display apparatus DDmay further include a window member (or structure) WM disposed on thepolarizing member PM, however, the window member WM may be omitted.

The display panel DP may generate an image, and provide the generatedimage to the front surface. The display panel DP may provide thegenerated image to a side in the third direction DR3. In one or moreexemplary embodiments, the display panel DP may be an organiclight-emitting display panel, however, exemplary embodiments are notlimited thereto or thereby. For instance, the display panel DP may be aliquid crystal display panel, a plasma display panel, an electrophoreticdisplay panel, a microelectromechanical system (MEMS) display panel, anelectrowetting display panel, and/or the like.

The display panel DP may be a flexible display panel. The display panelDP may include a flexible substrate. For the purposes of thisdisclosure, the term “flexible” refers to configurations that can beintentionally bent, and, thereby, has bending properties. In thismanner, the term “flexible” is not limited to a structure that may bebent and then fully folded, but may include a structure that is bent tothe level of several nanometers (nm).

Referring to FIG. 1B, the display panel DP may include a display panelbending part DP-BA corresponding to the bending area BA of the flexibledisplay apparatus DD, and a display panel non-bending part DP-NBA1 andDP-NBA2 corresponding to the non-bending area NBA of the flexibledisplay apparatus DD. The display panel bending part DP-BA, and thedisplay panel non-bending part DP-NBA1 and DP-NBA2 may be coupledtogether. In one or more exemplary embodiments, the display panelnon-bending part DP-NBA1 and DP-NBA2 may be provided in plurality. Forexample, the display panel non-bending part DP-NBA1 and DP-NBA2 mayinclude a first display panel non-bending part DP-NBA1 coupled to oneend of the display panel bending part DP-BA, and a second display panelnon-bending part DP-NBA2 coupled to the other end of the display panelbending part DP-BA.

As seen in FIG. 1B, the display panel non-bending parts DP-NBA1 andDP-NBA2 may be disposed respectively on both sides of the display panelbending part DP-BA with respect to the display panel bending part DP-BA.The display panel non-bending parts DP-NBA1 and DP-NBA2 may be disposedsymmetrically with respect to the display panel bending part DP-BA.However, exemplary embodiments are not limited thereto or thereby. Forinstance, the display panel non-bending parts DP-NBA1 and DP-NBA2 may bedisposed only on one side of the display panel bending part DP-BA. Asanother example, the display panel bending part DP-BA may be disposedbetween the display panel non-bending parts DP-NBA1 and DP-NBA2, but thedisplay panel bending part DP-BA may also be disposed to be lopsidedtoward one of the display panel non-bending parts DP-NBA1 and DP-NBA2.That is, the display panel bending part DP-BA may be off center orotherwise skewed to one side of the display panel DP. Also, the areas ofthe first display panel non-bending part DP-NBA1 and the second displaypanel non-bending part DP-NBA2 may be different from each other.

The polarizing member PM may be disposed on the display panel DP in theflexible display apparatus DD. The polarizing member PM may includeoptical members, such as a linear polarizer, a phase retardation layer,and an optical compensation layer. In one or more exemplary embodiments,the polarizing member PM may be disposed on an upper surface of thedisplay panel DP to be capable of reducing reflectivity of externallight provided from the outside, e.g., an ambient environment. Thepolarizing member PM may be a flexible polarizing member. The polarizingmember PM will be described in more detail later.

The window member WM may be disposed on the polarizing member PM. Thewindow member WM may protect the display panel DP, the polarizing memberPM, and/or the like. The window member WM may be a flexible window. Thewindow member WM may be composed of glass material or flexible plasticmaterial. However, exemplary embodiments are not limited thereto orthereby. For instance, any form of a general window member may be usedin association with exemplary embodiments. The window member WM may havea multilayer structure. The window member WM may have a multilayerstructure selected from a glass substrate, a plastic film, and a plasticsubstrate. The window member WM may further include a bezel pattern. Thewindow member WM may further include a surface protective layer (notillustrated). For example, a functional protective layer, such as a hardcoating layer, and an anti-fingerprint layer may further be included onthe window member WM.

The flexible display apparatus DD may be bent with respect to thebending axis BX in a first direction according to a first mode (see,e.g., FIG. 2A), bent with respect to the bending axis BX in a seconddirection according to a second mode (see, e.g., FIG. 3A), and may beunfolded in a third mode (see, e.g., FIG. 1A). The polarizing member PMmay be disposed, in the first mode, closer to the bending axis BX thanthe display panel DP. In the second mode, the polarizing member PM maybe disposed further away from the bending axis BX than the display panelDP.

It is noted that FIGS. 2A and 2B illustrate a state in which theflexible display apparatus DD is “in-folded” such that the displaysurface IS (see, e.g., FIG. 1A) of the flexible display apparatus DD ispositioned inside, e.g., closer to the bending axis BX than a surfaceopposing the display surface IS. That is, FIGS. 2A and 2B illustrate astate in which the flexible display apparatus is bent in the first mode.It is also noted that FIGS. 3A and 3B illustrate a state in which thedisplay apparatus is “out-folded” such that the display surface IS (see,e.g., FIG. 1A) of the flexible display apparatus DD is exposed outside,e.g., further from the bending axis BX than the surface opposing thedisplay surface IS. That is, FIGS. 3A and 3B illustrate a state in whichthe flexible display apparatus DD is bent in the second mode.

In FIG. 2B or FIG. 3B, a radius of curvature BR of the bending area BAof the flexible display apparatus DD may be greater than 0 mm and lessthan or equal to 5 mm. For example, the radius of curvature BR may be aradius of curvature formed by an inside surface of the bending area BAin a bent or folded state. For instance, the radius of curvature BR inthe flexible display apparatus DD may be from 1 mm to 5 mm inclusive.

According to one or more exemplary embodiments, the flexible displayapparatus DD may be configured to repeat operation modes illustratedonly in FIG. 1A and FIG. 2A, or only in FIG. 1A and FIG. 3A. However,exemplary embodiments are not limited thereto or thereby. For instance,the bending area BA may be defined to correspond to a mode in which auser manipulates the flexible display apparatus DD. Additionally, thearea of the bending area BA may not be fixed, but may be determineddepending on the radius of curvature BR.

Referring to FIGS. 1A, 1B, 2A, 2B, 3A, and 3B, the flexible displayapparatus DD may include the display panel DP having the bending area BAsuch that the flexible display apparatus DD is transformable into a bentshape or has a bent shape with respect to the bending axis BX extendingin one direction, and the polarizing member PM disposed on the displaypanel DP. In FIGS. 1A, 1B, 2A, 2B, 3A, and 3B, the one direction inwhich the bending axis BX extends is illustrated to be the seconddirection DR2, but exemplary embodiments are not limited thereto orthereby. For example, a direction in which the bending axis BX extendsmay be different according to a shape into which the flexible displayapparatus DD is transformed.

FIG. 4A is a perspective view illustrating a flexible display apparatusaccording to one or more exemplary embodiments. FIG. 4B is across-sectional view of the flexible display apparatus of FIG. 4A takenalong sectional line IV-IV′ according to one or more exemplaryembodiments. The flexible display apparatus of FIGS. 4A and 4B issimilar to the flexible display apparatus of FIGS. 1A, 1B, 2A, 2B, 3A,and 3B. As such, duplicative descriptions will be primarily omitted toavoid obscuring exemplary embodiments.

As seen in FIGS. 4A and 4B, the flexible display apparatus DD-1 mayinclude bending areas BA1 and BA2, and the non-bending area NBA. Each ofthe bending areas BA1 and BA2 may be bent from a corresponding side ofthe non-bending area NBA.

Referring to FIGS. 4A and 4B, the flexible display apparatus DD-1 mayinclude the non-bending area NBA in which the image IM is displayed on afirst (e.g., front) surface of the flexible display apparatus DD-1, anda first bending area BA1 and a second bending area BA2 in which theimage IM is displayed on second (e.g., side) surfaces of the flexibledisplay apparatus DD-1. The first bending area BA1 and the secondbending area BA2 may be bent respectively from opposing sides of thenon-bending area NBA. The first bending area BA1 and the second bendingarea BA2 may be areas bent respectively with respect to a first bendingaxis BX1 and a second bending axis BX2.

The first bending area BA1 bent with respect to the first bending axisBX1 may have a first radius of curvature BR1, and the second bendingarea BA2 bent with respect to the second bending axis BX2 may have asecond radius of curvature BR2. The first radius of curvature BR1 of thefirst bending area BA1 and the second radius of curvature BR2 of thesecond bending area BA2 may each be greater than 0 mm and less than orequal to 5 mm, such as 1 mm to 5 mm, inclusive. The first radius ofcurvature BR1 and the second radius of curvature BR2 may be equal to oneanother. Alternatively, the first radius of curvature BR1 and the secondradius of curvature BR2 may be different from each other.

Referring to FIGS. 4A and 4B, the non-bending area NBA may provide theimage IM in the third direction DR3 in which the front surface of theflexible display apparatus DD-1 faces. The first bending area BA1 mayprovide the image IM generally in a fifth direction DR5, whereas thesecond bending area BA2 may provide the image IM generally in a fourthdirection DR4. The fourth direction DR4 and the fifth direction DR5 maybe directions which cross the first to third directions DR1, DR2 andDR3. It is contemplated, however, that the directions indicated by thefirst to fifth directions DR1 to DR5 are relative, and, as such, are notlimited to or by the illustrated directional relationships.

The flexible display apparatus DD-1 may be a bendable display apparatusincluding the non-bending area NBA, and the bending areas BA1 and BA2disposed respectively on opposing sides of the non-bending area NBA.Alternatively, although not illustrated, the flexible display apparatusDD-1 may be a bendable display apparatus including one non-bending areaand one bending area. In this case, the one bending area may be providedto be bent only on one side of the one non-bending area.

FIG. 5 is a cross-sectional view illustrating a flexible displayapparatus according to one or more exemplary embodiments. It is notedthat FIG. 5 illustrates a cross-section of display apparatus DD-2corresponding to sectional line I-I′ of FIG. 1A. The flexible displayapparatus DD-2 of FIG. 5 is similar to the flexible display apparatus DDof FIGS. 1A and 1B, however, the flexible display apparatus DD-2 mayinclude the display panel DP, the polarizing member PM, a touch sensingunit (or structure) TSP, and the window member WM. The touch sensingunit TSP may be disposed on an upper surface or a lower surface of thepolarizing member PM. In other words, the touch sensing unit TSP may bedisposed between the window member WM and the polarizing member PM ordisposed between the polarizing member PM and the display panel DP.

As seen in FIG. 5 , the flexible display apparatus DD-2 includes thetouch sensing unit TSP disposed on the polarizing member PM. In otherwords, the flexible display apparatus DD-2 includes the display panelDP, the polarizing member PM disposed on the display panel DP, the touchsensing unit TSP disposed on the polarizing member PM, and the windowmember WM disposed on the touch sensing unit TSP.

Although not illustrated, the touch sensing unit TSP includes touchsensors and touch signal lines. The touch sensors and the touch signallines may have a single layer or multilayer structure. The touch sensorsand the touch signal lines may include any suitable material, such as,for instance, indium tin oxide (ITO), indium zinc oxide (IZO), zincoxide (ZnO), indium tin zinc oxide (ITZO), PEDOT, metal nanowire, orgraphene. The touch sensors and the touch signal lines may include ametal layer of, for example, molybdenum, silver, titanium, copper,aluminum, or an alloy thereof. The touch sensors and the touch signallines may have the same layer structure, or a different layer structurefrom one another.

Alternatively, unlike as shown in FIG. 5 , the touch sensing unit TSPmay be disposed between the display panel DP and the polarizing memberPM in the flexible display apparatus DD-2. The touch sensing unit TSPmay be disposed directly on the display panel DP.

For the purposes of this disclosure, the phrase “being disposed directlyon” excludes being attached using a separate adhesive member, and meansbeing formed by a continuous process. For example, in the case that thedisplay panel DP is an organic light-emitting display panel, the touchsensing unit TSP may be disposed directly on the organic light-emittingdisplay panel. That is, the touch sensing unit TSP may be disposeddirectly on an encapsulation layer of the organic light-emitting displaypanel.

Additionally, the window member WM of the flexible display apparatusDD-2 may be omitted. Although not illustrated, an adhesive member may bedisposed between the display panel DP and the polarizing member PM,between the polarizing member PM and the touch sensing unit TSP, orbetween the touch sensing unit TSP and the window member WM. In thiscase, the adhesive member may be an optically clear adhesive (OCA) film,or an optically clear adhesive resin (OCR) layer.

The polarizing member PM of the flexible display apparatuses DD, DD-1,and DD-2 will now be described in more detail below with reference toFIGS. 6, 7A to 7C, and 8 . It is noted, however, that the variouspolarizing members of FIGS. 6, 7A to 7 C, and 8 will be distinguishedfrom one another through different call reference numbers, but any oneof the polarizing members of FIGS. 6,4 7A to 7C, and 8 may be utilizedas the polarizing member PM of FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, and5 .

FIG. 6 is a cross-sectional view illustrating a polarizing member of aflexible display apparatus according to one or more exemplaryembodiments. Referring to FIG. 6 , the polarizing member PM may includea linear polarizer PP, a λ/4 phase retardation layer RC1, and a firstadhesive member (or layer) AP1. The λ/4 phase retardation layer RC1 maybe disposed most adjacent to the display panel DP (see, e.g., FIG. 1B)than other layers of the polarizing member PM. In one or more exemplaryembodiments, the λ/4 phase retardation layer RC1, the first adhesivemember AP1, and the linear polarizer PP may be disposed to besequentially laminated (or otherwise stacked) in the third directionDR3.

The linear polarizer PP may linearly polarize light propagating in adirection. The linear polarizer PP may be a film-type polarizerincluding a stretched polymer film. For example, the stretched polymerfilm may be a stretched polyvinyl alcohol-based film, however, exemplaryembodiments are not limited thereto or thereby. In one or more exemplaryembodiments, the linear polarizer PP may be manufactured by adsorbingdichroic dye on the stretched polymer film. For example, the linearpolarizer PP may be manufactured by adsorbing iodine on a stretchedpolyvinyl alcohol film. In this case, a direction in which the polymerfilm is stretched may be an absorption axis of the linear polarizer PP,and a direction perpendicular to the direction in which the polymer filmis stretched may be a transmission axis of the linear polarizer PP.

Although not illustrated, the linear polarizer PP may further include atleast one protective layer. For example, a triacetyl cellulose (TAC)layer may further be included on at least one of an upper surface and alower surface of the linear polarizer PP. Exemplary embodiments,however, are not limited thereto or thereby. For instance, the linearpolarizer PP may further include, as the protective layer, a hardcoating layer, an anti-reflective layer, an anti-glare layer, and/or thelike.

The polarizing member PM may include the λ/4 phase retardation layer RC1disposed on a lower surface of the linear polarizer PP. The λ/4 phaseretardation layer RC1 may be an optical layer for retarding the phase ofprovided light by λ/4. For example, when the wavelength of light thathas passed through the linear polarizer PP and is provided to the λ/4phase retardation layer RC1 is 550 nm, the light having passed throughthe λ/4 phase retardation layer RC1 may have a phase retardation valueof 137.5 nm.

Additionally, the λ/4 phase retardation layer RC1 may have opticalanisotropy, and change a polarization state of light incident on the λ/4phase retardation layer RC1. In other words, light that has passedthrough the linear polarizer PP and is provided to the λ/4 phaseretardation layer RC1 may change from a linear polarization state to acircular polarization state. Alternatively, light provided to the λ/4phase retardation layer RC1 with a circular polarization state maychange to a linear polarization state.

In one or more exemplary embodiments, the λ/4 phase retardation layerRC1 may be an A-plate. That is, when a refractive index of the λ/4 phaseretardation layer RC1 in the first direction DR1 is defined as a firstrefractive index n1, a refractive index in the second direction DR2 isdefined as a second refractive index n2, and a refractive index in thethird direction DR3 is defined as a third refractive index n3, the firstto third refractive indices n1 to n3 may satisfy Equation 1, as shownbelow.

n1≠n2≈n3  Equation 1

The second and third refractive indices n2 and n3 may be substantiallyequal to one another. However, exemplary embodiments are not limitedthereto or thereby. For instance, and the second and third refractiveindices n2 and n3 may be different from each other.

A phase retardation layer, such as the λ/4 phase retardation layer RC1,may have an in-plane phase retardation value Re, and a phase retardationvalue Rth in a thickness direction. The in-plane phase retardation valueRe, and the phase retardation value Rth in the thickness direction maybe calculated (or otherwise determined) according to Equation 2. It isnoted that d in Equation 2 represents the thickness of the phaseretardation layer.

$\begin{matrix}{{{Re} = {\left( {{n1} - {n2}} \right)*d}}{{Rth} = {\left( {\frac{\left( {{n1} + {n2}} \right)}{2} - {n3}} \right)*d}}} & {{Equation}2}\end{matrix}$

The phase retardation value Rth in the thickness direction may becompensated for by further including an optical compensation layer inthe polarizing member PM. The optical compensation layer may be aC-plate. The optical compensation layer will be described in more detaillater.

The λ/4 phase retardation layer RC1 may be a liquid crystal coatinglayer in the polarizing member PM. The λ/4 phase retardation layer RC1may be a liquid crystal coating layer manufactured using a reactiveliquid crystal monomer. The λ/4 phase retardation layer RC1 may bemanufactured through a process of polymerizing after coating andaligning a reactive liquid crystal monomer. For example, the liquidcrystal monomer used in the λ/4 phase retardation layer RC1 may have arod-shaped nematic phase. That is, the λ/4 phase retardation layer RC1may be a nematic liquid crystal coating layer.

The λ/4 phase retardation layer RC1 may be composed of a liquid crystalcoating layer only without a base substrate that is typically utilizedas a support. The total thickness of a flexible display apparatus (e.g.,flexible display apparatus DD) may be reduced by using, in thepolarizing member PM, the λ/4 phase retardation layer RC1 composed ofthe liquid crystal coating layer only without including the basesubstrate. In other words, the thickness of the polarizing member PM maybe reduced by using the λ/4 phase retardation layer RC1 that is theliquid crystal coating layer, and, as such, the flexible displayapparatus may be bent more easily.

A thickness t_(R1) of the λ/4 phase retardation layer RC1 that is theliquid crystal coating layer may be from 0.5 μm to 5 μm inclusive. Forinstance, the thickness t_(R1) of the λ/4 phase retardation layer RC1may be from 0.5 μm to 2 μm inclusive. When the thickness t_(R1) of theλ/4 phase retardation layer RC1 becomes smaller than 0.5 μm, theimplementation of optical properties may not be uniform in the λ/4 phaseretardation layer RC1, and when the thickness t_(R1) of the λ/4 phaseretardation layer RC1 becomes larger than 5 μm, a thickness reductioneffect of the polarizing member PM may be insufficient. In other words,when the thickness t_(R1) of the λ/4 phase retardation layer RC1 becomeslarger than 5 μm, flexibility in a flexible display apparatus DD may notbe satisfactory, and, in this manner, a crack may occur within the λ/4phase retardation layer RC1 and display quality may be degraded.

The first adhesive member AP1 may be disposed between the λ/4 phaseretardation layer RC1 and the linear polarizer PP. The first adhesivemember AP1 may be an adhesive layer with a glass transition temperatureTg from 40° C. to 150° C. inclusive. Given that the first adhesivemember AP1 has a glass transition temperature higher than roomtemperature, bonding strength between the λ/4 phase retardation layerRC1 and the linear polarizer PP may be increased. Additionally, byforming the first adhesive member AP1 with an adhesive layer having arelatively high glass transition temperature, deformation may beminimized when the first adhesive member AP1 is folded or bent under thecondition of room temperature or relatively high temperature. Also,deformation of the λ/4 phase retardation layer RC1 adjacent to the firstadhesive member AP1 may also be minimized or at least reduced.

The first adhesive member AP1 may be an adhesive layer cross-linkedthrough an ultraviolet curing or heat curing process. The first adhesivemember AP1 may be an adhesive layer including at least one among anacrylic resin, a silicone resin, a urethane resin, and an epoxy resin.

The first adhesive member AP1 may include an ultraviolet curableadhesive. The first adhesive member AP1 may be an adhesive layer formedby polymerizing and curing through at least one reaction of radicalpolymerization and cationic polymerization.

The adhesive layer constituting the first adhesive member AP1 may beformed with an adhesive composition including a cationic polymerizablecompound. For example, the adhesive composition may include at least oneamong an epoxy compound, a vinyl ether compound, an oxetane compound, anoxolane compound, a cyclic acetal compound, a cyclic lactone compound, athiirane compound, a thio vinyl ether compound, a spirorthoestercompound, an ethylene unsaturated compound, a cyclic ether compound, anda cyclic thioether compound. Alternatively (or additionally), theadhesive layer constituting the first adhesive member AP1 may be formedwith an adhesive composition including a radical polymerizable compoundhaving a radical polymerization reactor. For example, the radicalpolymerizable compound may be an acrylic compound, and specifically, amethacrylate compound.

The adhesive composition forming the first adhesive member AP1 mayinclude photoinitiator, and/or the like. Additionally, the adhesivecomposition may further include an additive, such as a photosensitizer,a silane coupling agent, a plasticizer, and a defoaming agent inaddition to the photoinitiator.

A thickness t_(A1) of the first adhesive member AP1 may be from 0.1 μmto 5 μm inclusive. For instance, the thickness t_(A1) of the firstadhesive member AP1 may be from 0.5 μm to 3 μm inclusive. When thethickness t_(A1) of the first adhesive member AP1 is smaller than 0.1μm, adhesive strength for bonding the linear polarizer PP and the λ/4phase retardation layer RC1 together may not be obtained, and, as such,peeling of the first adhesive member AP1 may occur when the flexibledisplay apparatus is bent. Additionally, when the thickness t_(A1) ofthe first adhesive member AP1 becomes larger than 5 μm, a thicknessreduction effect of the polarizing member PM may be insufficient, and acrack may occur in the λ/4 phase retardation layer RC1 adjacent to thefirst adhesive member AP1 under a high temperature reliability 3condition. As such, display quality may be reduced.

The sum of the thickness t_(A1) of the first adhesive member AP1 and thethickness t_(R1) of the λ/4 phase retardation layer RC1 may be less thanor equal to a thickness t_(P) of the linear polarizer PP. In otherwords, in one or more exemplary embodiments, the total thickness of thepolarizing member PM may be reduced by forming the λ/4 phase retardationlayer RC1 with a liquid crystal coating layer, and forming the firstadhesive member AP1 with an adhesive composition.

Alternatively, the first adhesive member AP1 may be formed with anadhesive layer with a glass transition temperature from 40° C. to 150°C. inclusive so as to maintain adhesive strength between the linearpolarizer PP and the λ/4 phase retardation layer RC1. Additionally, whenthe flexible display apparatus (e.g., flexible display apparatus DD) isfolded or bent, deformation of the first adhesive member AP1 may notoccur, and, as such, deformation of the λ/4 phase retardation layer RC1adjacent thereto may be prevented (or at least reduced), therebyalleviating display quality degradation due to the deformation of theλ/4 phase retardation layer RC1 of the flexible display apparatus.

It is also contemplated that the polarizing member PM, in one or moreexemplary embodiments, may include the linear polarizer PP and the λ/4phase retardation layer RC1, and the polarizing member PM may bedisposed on the display panel DP (see, e.g., FIG. 1B), thereby 21reducing external light reflectivity of the flexible display apparatus,such as flexible display apparatus DD (see, e.g., FIG. 1B).

FIGS. 7A, 7B, 7C, and 8 are cross-sectional views illustratingpolarizing members of flexible display apparatuses according to variousexemplary embodiments. In one or more exemplary embodiments, thepolarizing member PM may further include at least one optical layer inaddition to the λ/4 phase retardation layer RC1 and the linear polarizerPP. Hereinafter, when a polarizing member PM of FIGS. 7A to 7C and 8 aredescribed, duplicative descriptions will be primarily omitted to avoidobscuring exemplary embodiments, and differences will be mainlydescribed.

Referring to FIG. 7A, the polarizing member PM-1 may further include aλ/2 phase retardation layer RC2 in addition to the λ/4 phase retardationlayer RC1 and the linear polarizer PP. The λ/2 phase retardation layerRC2 may be disposed between the λ/4 phase retardation layer RC1 and thelinear polarizer PP. That is, the λ/2 phase retardation layer RC2 may bedisposed between the first adhesive member AP1 and the linear polarizerPP. In addition, a second adhesive member AP2 may be further includedbetween the λ/2 phase retardation layer RC2 and the linear polarizer PP.

The λ/2 phase retardation layer RC2 may be an optical layer forretarding the phase of provided light by λ/2. For example, when thewavelength of light that has passed through the linear polarizer PP, andis provided to the λ/2 phase retardation layer RC2 is 550 nm, the lighthaving passed through the λ/2 phase retardation layer RC2 may have aphase retardation value of 275 nm. Additionally, the λ/2 phaseretardation layer RC2 may change a polarization state of light incidenton the λ/2 phase retardation layer RC2. A polarization direction oflinearly polarized light may change which has been incident on the λ/2phase retardation layer RC2 from the linear polarizer PP.

One among a phase retardation value of the λ/4 phase retardation layerRC1 in a thickness direction, and a phase retardation value of the λ/2phase retardation layer RC2 in the thickness direction may have apositive value, and the other may have a negative value. For example,the λ/4 phase retardation layer RC1 may be a positive A-plate, and theλ/2 phase retardation layer RC2 may be a negative A-plate.

In Equation 1 provided above, a case that n1>n2 is referred to as thepositive A-plate, and a case that n1<n2 is referred to as the negativeA-plate. Accordingly, in the case of the positive A-plate, a phaseretardation value in the thickness direction may have a positive value,and in the case of the negative A-plate, a phase retardation value inthe thickness direction may have a negative value. Accordingly, when thepolarizing member PM includes both the λ/4 phase retardation layer RC1and the λ/2 phase retardation layer RC2 that have been laminated, aphase difference in the thickness direction may be offset and decreased.Thus, according to one or more exemplary embodiments, a change in thephase difference according to a viewing angle may be decreased becausephase retardation values of the λ/4 phase retardation layer RC1 and theλ/2 phase retardation layer RC2 in the thickness direction havepolarities different from each other. As a result, color shift may bereduced, resulting in display quality improvement.

The λ/2 phase retardation layer RC2 may be a liquid crystal coatinglayer. The λ/2 phase retardation layer RC2 may be a liquid crystalcoating layer manufactured using a reactive liquid crystal monomer. Theλ/2 phase retardation layer RC2 may be manufactured through a process ofpolymerizing after coating and aligning the reactive liquid crystalmonomer. For example, the liquid crystal monomer used in the λ/2 phaseretardation layer RC2 may have a disc-shaped discotic phase. That is,the λ/2 phase retardation layer RC2 may be a discotic liquid crystalcoating layer.

The λ/2 phase retardation layer RC2 may be composed of a liquid crystalcoating layer only without a base substrate that is typically utilizedas a support. The total thickness of a flexible display apparatus (e.g.,flexible display apparatus DD) may be reduced by including, in thepolarizing member PM, the λ/2 phase retardation layer RC2 composed ofthe liquid crystal coating layer only without including a basesubstrate. In other words, the thickness of the polarizing member PM maybe reduced by using the λ/2 phase retardation layer RC2 that is theliquid crystal coating layer, and, as such, the flexible displayapparatus may be bent more easily.

A thickness t_(R2) of the λ/2 phase retardation layer RC2 that is theliquid crystal coating layer may be from 0.5 μm to 5 μm inclusive. Forexample, the thickness t_(R2) of the λ/2 phase retardation layer RC2 maybe from 0.5 μm to 2 μm inclusive. Additionally, the thickness t_(R2) ofthe λ/2 phase retardation layer RC2 may be equal to or different fromthe thickness t_(R1) of the λ/4 phase retardation layer RC1. Thethickness t_(R2) of the λ/2 phase retardation layer RC2 may be greaterthan the thickness t_(R1) of the λ/4 phase retardation layer RC1.

When the thickness t_(R2) of the λ/2 phase retardation layer RC2 becomessmaller than 0.5 μm, the implementation of optical properties may not beuniform in the λ/2 phase retardation layer RC2, and when the thicknesst_(R2) of the λ/2 phase retardation layer RC2 becomes larger than 5 μm,a thickness reduction effect of the polarizing member PM may beinsufficient. In other words, when the thickness t_(R2) of the λ/2 phaseretardation layer RC2 becomes larger than 5 μm, a crease or a crack mayoccur within the λ/2 phase retardation layer RC2 under a folding orbending condition. This may degrade display quality.

The second adhesive member AP2 may be disposed between the λ/2 phaseretardation layer RC2 and the linear polarizer PP so as to bond the λ/2phase retardation layer RC2 and the linear polarizer PP together. Thesecond adhesive member AP2 may be a pressure sensitive adhesive layerwith a glass transition temperature from −35° C. to 0° C. inclusive, oran adhesive layer with a glass transition temperature from 40° C. to150° C. inclusive.

In one or more exemplary embodiments, because the pressure sensitiveadhesive layer has a glass transition temperature lower than roomtemperature, the pressure sensitive adhesive layer may correspond to anadhesive member having tackiness at room temperature. In this manner,because the adhesive layer has a glass transition temperature higherthan room temperature, the adhesive layer may correspond to an adhesivemember without tackiness at room temperature. The pressure sensitiveadhesive layer may be an adhesive member having a relatively low modulusvalue compared with the adhesive layer.

The pressure sensitive adhesive layer may be formed of a pressuresensitive adhesive composition including at least one among an acrylicpressure sensitive adhesive, a silicone pressure sensitive adhesive, anepoxy pressure sensitive adhesive, and a rubber pressure sensitiveadhesive. The pressure sensitive adhesive composition may furtherinclude an additive, such as a silane coupling agent, a tackifyingresin, a hardener, an ultraviolet stabilizer, an antioxidant, and afiller.

The adhesive layer may be formed of an adhesive composition including atleast one among an acrylic resin, a silicone resin, a urethane resin,and an epoxy resin. For example, the adhesive layer and the pressuresensitive adhesive layer may all be formed of an acrylic compound, butmay be adhesive members having degrees of polymerization different fromeach other, or degrees of cross-linking different from each other.

For example, when the second adhesive member AP2 is the pressuresensitive adhesive layer, the second adhesive member AP2 may have asofter property at room temperature than the first adhesive member AP1.When the second adhesive member AP2 is the pressure sensitive adhesivelayer, the second adhesive member AP2 may have a smaller modulus thanthe first adhesive member AP1. A glass transition temperature of thesecond adhesive member AP2 may be lower than that of the first adhesivemember AP1.

When the second adhesive member AP2 is the adhesive layer, the secondadhesive member AP2 may have a modulus value equal to that of the firstadhesive member AP1. Alternatively, the second adhesive member AP2 maybe an adhesive layer having a modulus value different from that of thefirst adhesive member AP1. Both the second adhesive member AP2 and thefirst adhesive member AP1 may have glass transition temperatures higherthan room temperature, and may correspond to a non-sticky adhesivemembers at room temperature.

A thickness t_(A2) of the second adhesive member AP2 may be from 0.1 μmto 5 μm inclusive. For instance, the thickness t_(A2) of the secondadhesive member AP2 may be from 0.5 μm to 3 μm inclusive. When thethickness t_(A2) of the second adhesive member AP2 is smaller than 0.1μm, adhesive strength for bonding the linear polarizer PP and the λ/2phase retardation layer RC2 together may not be obtained, and, as such,peeling of the second adhesive member AP2 may occur when the flexibledisplay apparatus, e.g., flexible display apparatus DD, is bent.Additionally, when the thickness t_(A2) of the second adhesive memberAP2 becomes larger than 5 μm, a thickness reduction effect of thepolarizing member PM may be insufficient. Additionally, when thethickness t_(A2) of the second adhesive member AP2 becomes larger than 5μm, a crease or a crack may occur in the second adhesive member AP2under a bending or folding condition.

The thickness t_(P) of the linear polarizer PP may be greater than orequal to the sum of the thickness t_(R2) of the λ/2 phase retardationlayer RC2, the thickness t_(A2) of the second adhesive member AP2, thethickness t_(R1) of the λ/4 phase retardation layer RC1, and thethickness t_(A1) of the first adhesive member AP1.

Referring to FIG. 7B, the polarizing member PM-2 may further include afirst optical compensation layer CP1 in addition to the λ/4 phaseretardation layer RC1, the linear polarizer PP, and the λ/2 phaseretardation layer RC2. The first optical compensation layer CP1 may bedisposed on a lower surface of the λ/4 phase retardation layer RC1. Thatis, the first optical compensation layer CP1 may be disposed mostadjacent to the display panel DP (see, e.g., FIG. 1B) among the variouslayers of the polarizing member PM-2. In one or more exemplaryembodiments, the polarizing member PM may include the first opticalcompensation layer CP1, the λ/4 phase retardation layer RC1, the λ/2phase retardation layer RC2, and the linear polarizer PP disposed to belaminated (or stacked) in the third direction DR3.

The first optical compensation layer CP1 may be an optical functionallayer for compensating for the phase retardation value Rth in thethickness direction of the λ/4 phase retardation layer RC1. The firstoptical compensation layer CP1 may be a C-plate. For instance, when arefractive index of the first optical compensation layer CP1 in thefirst direction DR1 is defined as a first refractive index n1, arefractive index in the second direction DR2 is defined as a secondrefractive index n2, and a refractive index in the third direction DR3is defined as a third refractive index n3, the first to third refractiveindices n1 to n3 may satisfy Equation 3, as shown below.

n1≈n2≠n3  Equation 3

In the first optical compensation layer CP1, the first and secondrefractive indices n1 and n2 may be substantially equal. However,exemplary embodiments are not limited thereto or thereby. For instance,the first and second refractive indices n1 and n2 may be different fromeach other.

The first optical compensation layer CP1 may be a negative C-plate or apositive C-plate. For example, when the λ/4 phase retardation layer RC1has a phase retardation value Rth in the thickness direction with anegative value, the first optical compensation layer CP1 may be apositive C-plate, and when the λ/4 phase retardation layer RC1 has aphase retardation value Rth in the thickness direction with a positivevalue, the first optical compensation layer CP1 may be a negativeC-plate. The first optical compensation layer CP1 may be a form of asolidified layer or a cured layer of a liquid crystal compositionincluding a liquid crystal compound. Alternatively, the first opticalcompensation layer CP1 may be provided in a film type.

A third adhesive member AP3 may be disposed between the first opticalcompensation layer CP1 and the λ/4 phase retardation layer RC1. Thethird adhesive member AP3 may be a pressure sensitive adhesive layerwith a glass transition temperature from −35° C. to 0° C. inclusive, oran adhesive layer with a glass transition temperature from 40° C. to150° C. inclusive. For the third adhesive member AP3, the same contentas described with respect to the second adhesive member AP2 of FIG. 7Amay be applied.

In the polarizing member PM-2 illustrated in FIG. 7B, the first adhesivemember AP1 may be an adhesive layer with a glass transition temperaturefrom 40° C. to 150° C. inclusive, and the second adhesive member AP2 andthe third adhesive member AP3 may be pressure sensitive adhesive layerswith a glass transition temperature from −35° C. to 0° C. inclusive, oradhesive layers with a glass transition temperatures from 40° C. to 150°C. inclusive. For example, one of the second adhesive member AP2 and thethird adhesive member AP3 may be the pressure sensitive adhesive layer,and the other may be the adhesive layer. Alternatively, both the secondadhesive member AP2 and the third adhesive member AP3 may be theadhesive layers, or both the second adhesive member AP2 and the thirdadhesive member AP3 may be the pressure sensitive adhesive layers.

The polarizing member PM-3 included in an embodiment illustrated in FIG.7C may further include a second optical compensation layer CP2 and afourth adhesive member AP4 when compared with the polarizing member PM-2in FIG. 7B. The second optical compensation layer CP2 may be disposed ona lower surface of the λ/2 phase retardation layer RC2. The secondoptical compensation layer CP2 may be disposed between the λ/4 phaseretardation layer RC1 and the λ/2 phase retardation layer RC2. Thesecond optical compensation layer CP2 may be disposed between the firstadhesive member AP1 and the λ/2 phase retardation layer RC2. The fourthadhesive member AP4 may be disposed between the second opticalcompensation layer CP2 and the λ/2 phase retardation layer RC2. Thefourth adhesive member AP4 may bond the second optical compensationlayer CP2 and the λ/2 phase retardation layer RC2 together. The fourthadhesive member AP4 may be an adhesive layer with a glass transitiontemperature from 40° C. to 150° C. inclusive.

The second optical compensation layer CP2 may be disposed on the lowersurface of the λ/2 phase retardation layer RC2 so as to compensate forthe phase retardation value Rth in the thickness direction of the λ/2phase retardation layer RC2. The second optical compensation layer CP2may be a C-plate. The second optical compensation layer CP2 may be anegative C-plate or a positive C-plate. For example, when the λ/2 phaseretardation layer RC2 has a phase retardation value Rth in the thicknessdirection with a negative value, the second optical compensation layerCP2 may be the positive C-plate, and when the λ/2 phase retardationlayer RC2 has a phase retardation value Rth in the thickness directionwith a positive value, the second optical compensation layer CP2 may bethe negative C-plate. The second optical compensation layer CP2 may be aform of a solidified layer or a cured layer of a liquid crystalcomposition including a liquid crystal compound.

In the polarizing member PM-3 illustrated in FIG. 7C, the first adhesivemember AP1 and the fourth adhesive member AP4 may be adhesive layerswith a glass transition temperature from 40° C. to 150° C. inclusive,and the second adhesive member AP2 and the third adhesive member AP3 maybe pressure sensitive adhesive layers with a glass transitiontemperature from −35° C. to 0° C. inclusive, or adhesive layers with aglass transition temperature from 40° C. to 150° C. inclusive. Forexample, one of the second adhesive member AP2 and the third adhesivemember AP3 may be the pressure sensitive adhesive layer, and the othermay be the adhesive layer. Alternatively, both the second adhesivemember AP2 and the third adhesive member AP3 may be the adhesive layers,or both the second adhesive member AP2 and the third adhesive member AP3may be the pressure sensitive adhesive layers.

The polarizing member PM-4 illustrated in FIG. 8 may include the firstoptical compensation layer CP1, the λ/4 phase retardation layer RC1, andthe linear polarizer PP. The polarizing member PM-4 illustrated in FIG.8 may not be provided with the λ/2 phase retardation layer RC2 and thesecond adhesive member AP2, as compared with the polarizing member PM-2of FIG. 7B. That is, referring to FIG. 8 , the first opticalcompensation layer CP1 may be disposed most adjacent to the displaypanel DP (see, e.g., FIG. 1B), and may be disposed on a lower surface ofthe λ/4 phase retardation layer RC1. The third adhesive member AP3 maybe disposed between the first optical compensation layer CP1 and the λ/4phase retardation layer RC1.

The first optical compensation layer CP1 may be a C-plate forcompensating for the phase retardation value Rth in the thicknessdirection of the λ/4 phase retardation layer RC1. The first opticalcompensation layer CP1 may be a negative C-plate or a positive C-plate.For example, when the λ/4 phase retardation layer RC1 has a phaseretardation value Rth in the thickness direction with a negative value,the first optical compensation layer CP1 may be the positive C-plate,and when the λ/4 phase retardation layer RC1 has a phase retardationvalue Rth in the thickness direction with a positive value, the firstoptical compensation layer CP1 may be the negative C-plate. The firstoptical compensation layer CP1 may be a form of a solidified layer or acured layer of a liquid crystal composition including a liquid crystalcompound.

The third adhesive member AP3 may be an adhesive member for bonding thefirst optical compensation layer CP1 and the λ/4 phase retardation layerRC1 together. Accordingly, the polarizing member PM-4 may include thefirst optical compensation layer CP1, the third adhesive member AP3, theλ/4 phase retardation layer RC1, the first adhesive member AP1, and thelinear polarizer PP sequentially laminated in the third direction DR3.The third adhesive member AP3 may be a pressure sensitive adhesive layerwith a glass transition temperature from −35° C. to 0° C. inclusive, oran adhesive layer with a glass transition temperature from 40° C. to150° C. inclusive. For the first optical compensation layer CP1 and thethird adhesive member AP3, the description provided in association withFIGS. 7A to 7C may be applied.

For the polarizing member PM included in a flexible display apparatus(e.g., flexible display apparatus DD), such as the polarizing membersillustrated in FIGS. 6, 7A to 7C, and 8, deformation of the λ/4 phaseretardation layer RC1 may be prevented (or at least reduced) by formingthe first adhesive member AP1 adjacent to the λ/4 phase retardationlayer RC1 with an adhesive layer with a glass transition temperaturefrom 40° C. to 150° C. inclusive such that the first adhesive member AP1functions as a supporting layer for the λ/4 phase retardation layer RC1when the flexible display apparatus is folded or bent. In this manner,there may be an effect of improved display quality of a flexible displayapparatus because the λ/4 phase retardation layer RC1 may maintainoptical properties irrespective of the operating conditions of theflexible display apparatus.

FIG. 9 illustrates a relationship between optical axes of opticalmembers included in a polarizing member according to one or moreexemplary embodiments.

For instance, FIG. 9 schematically illustrates a relationship betweenoptical axes of the linear polarizer PP, the λ/4 phase retardation layerRC1, and the λ/2 phase retardation layer RC2 in the polarizing memberPM-1. FIG. 9 illustrates a relationship between an absorption axis PP-OXof the linear polarizer PP, a first optical axis RX1 of the λ/4 phaseretardation layer RC1, and a second optical axis RX2 of the λ/2 phaseretardation layer RC2 when viewed in a plan view, e.g., when viewed inthe third direction DR3. In other words, FIG. 9 illustrates therelationship between the absorption axis PP-OX of the linear polarizerPP, the first optical axis RX1 of the λ/4 phase retardation layer RC1,and the second optical axis RX2 of the λ/2 phase retardation layer RC2projected onto a plane parallel to a plane defined by the axis of thefirst direction DR1 and the axis of the second direction DR2. Forexample, the plane parallel to the plane defined by the axis of thefirst direction DR1 and the axis of the second direction DR2 in FIG. 9may be parallel to the display panel DP.

The first optical axis RX1 of the λ/4 phase retardation layer, and thesecond optical axis RX2 of the λ/2 phase retardation layer mayrespectively represent slow axes of the λ/4 phase retardation layer RC1(see FIG. 7A), and the λ/2 phase retardation layer RC2 (see, e.g., FIG.7A).

In one or more exemplary embodiments, an angle θ1 between the absorptionaxis PP-OX of the linear polarizer PP and the bending axis BX may be45±30 degrees. An angle θ2 between the absorption axis PP-OX of thelinear polarizer PP and the first optical axis RX1 of the λ/4 phaseretardation layer RC1 may be 75±30 degrees. Additionally, an angle θ3between the absorption axis PP-OX of the linear polarizer PP and thesecond optical axis RX2 of the λ/2 phase retardation layer RC2 may be15±13 degrees. For example, θ1 may be 45 degrees, θ2 may be 75 degrees,and θ3 may be 15 degrees. Additionally, an angle between the firstoptical axis RX1 of the λ/4 phase retardation layer RC1 and the secondoptical axis RX2 of the λ/2 phase retardation layer RC2 may be 60±30degrees. For example, the angle between the first optical axis RX1 andthe second optical axis RX2 may be 60 degrees.

Furthermore, FIG. 9 is illustrated about the bending axis BX as anexample of the flexible display apparatus DD illustrated in FIG. 1A, butthe illustration may also be applied to the bending axes BX1 and BX2illustrated in FIG. 4B in the same way. In FIG. 9 , the absorption axisPP-OX is illustrated, by way of example, to have revolvedcounterclockwise with respect to the bending axis BX, but is not limitedthereto or thereby. For example, the absorption axis PP-OX may revolveclockwise with respect to the bending axis BX, and, also in this case,the angle θ1 between the absorption axis PP-OX and the bending axis BXmay be 45±30 degrees. In other words, the angle θ1 between theabsorption axis PP-OX and the bending axis BX may have a value between15 degrees and 75 degrees, and for instance, may have 45 degrees.

The absorption axis PP-OX of the linear polarizer PP and the bendingaxis BX are illustrated to have an angle therebetween of 45±30 degreesin FIG. 9 , but exemplary embodiments are not limited thereto orthereby. For example, the absorption axis PP-OX of the linear polarizerPP and the bending axis BX may correspond, or may be perpendicular toeach other when viewed in a plane. For instance, the angle θ1 betweenthe absorption axis PP-OX of the linear polarizer PP and the bendingaxis BX may be 0±30 degrees or 90±30 degrees.

When the angle θ1 between the absorption axis PP-OX and the bending axisBX is 0 degrees, the transmission axis (not illustrated) of the linearpolarizer PP perpendicular to the absorption axis PP-OX may beperpendicular to the bending axis BX, and a bending motion may breakmolecular binding in a direction of the transmission axis (notillustrated), thereby causing a crack. Alternatively, when the angle θ1between the absorption axis PP-OX and the bending axis BX is 90 degrees,the probability is relatively reduced that the molecular binding in thedirection of the transmission axis (not illustrated) is broken, butwearing polarized sunglasses, or the like may cause a phenomenon that animage is not viewed at a specific position to occur, and additionally aphenomenon may occur that the linear polarizer PP is physically torn inthe direction of the transmission axis (not illustrated). According toone or more exemplary embodiments, the angle θ1 between the absorptionaxis PP-OX and the bending axis BX has a value from 15 degrees to 75degrees inclusive, and as such, bending properties may be furtherimproved. In addition, the phenomenon that the molecular binding in thedirection of the transmission axis (not illustrated) is broken, thephenomenon that the linear polarizer PP is physically torn in thedirection of the transmission axis (not illustrated), and the phenomenonthat an image is not viewed at a specific position when wearingpolarized sunglasses, or the like, may be decreased.

The relationship between the absorption axis PP-OX of the linearpolarizer PP, the first optical axis RX1, and the second optical axisRX2 is illustrated in FIG. 9 , but exemplary embodiments are not limitedthereto or thereby. For example, the same relationship may be appliedalso between the transmission axis (not illustrated) of the linearpolarizer PP, the first optical axis RX1, and the second optical axisRX2. For instance, an angle between the transmission axis (notillustrated) of the linear polarizer PP, and the first optical axis RX1of the λ/4 phase retardation layer RC1 may be 75±30 degrees. Inaddition, an angle between the transmission axis (not illustrated) ofthe linear polarizer PP, and the second optical axis RX2 of the λ/2phase retardation layer RC2 may be 15±13 degrees. Additionally, an anglebetween the transmission axis (not illustrated) of the linear polarizerPP, and the bending axis BX may be 45±30 degrees. For instance, theangle between the transmission axis (not illustrated) of the linearpolarizer PP and the bending axis BX may be 45 degrees, the anglebetween the transmission axis (not illustrated) of the linear polarizerPP and the first optical axis RX1 may be 75 degrees, and the anglebetween the transmission axis (not illustrated) of the linear polarizerPP and the second optical axis RX2 may be 15 degrees.

When the polarizing member PM includes the linear polarizer PP and theλ/4 phase retardation layer RC1, but does not include the λ/2 phaseretardation layer RC2 as illustrated in FIG. 6 , the angle θ2 betweenthe absorption axis PP-OX of the linear polarizer PP, and the firstoptical axis RX1 of the λ/4 phase retardation layer RC1 may be 45±30degrees when viewed in a plane. Additionally, the angle θ2 between thetransmission axis (not illustrated) of the linear polarizer PP and thefirst optical axis RX1 of the λ/4 phase retardation layer RC1 may be45±30 degrees. For example, the angle θ2 between the absorption axisPP-OX or the transmission axis (not illustrated) of the linear polarizerPP and the first optical axis RX1 of the λ/4 phase retardation layer RC1may be 45 degrees.

Table 1 shows results of a folding test for a flexible display apparatusof an exemplary embodiment. A polarizing member PM used for the foldingtest has a structure of the polarizing member PM-1 illustrated in FIG.7A. Comparative Example in Table 1 includes a polarizing member PM-1 inwhich all of two adhesive members AP1 and AP2 (see FIG. 7A) are pressuresensitive adhesive layers with a glass transition temperature from −35°C. to 0° C. inclusive. Embodiment 1 includes a polarizing member PM-1 inwhich the first adhesive member AP1 (see FIG. 7A) is an adhesive layerwith a glass transition temperature from 40° C. to 150° C. inclusive,and the second adhesive member AP2 (see FIG. 7A) is a pressure sensitiveadhesive layer with a glass transition temperature from −35° C. to 0° C.inclusive. Embodiment 2 includes a polarizing member PM-1 in which allof the first adhesive member AP1 (see FIG. 7A) and the second adhesivemember AP2 (see FIG. 7A) are adhesive layers with a glass transitiontemperature from 40° C. to 150° C. inclusive.

Additionally, “in-folding” condition of “test condition” represents astate that the flexible display apparatus DD is folded as illustrated inFIG. 2A, and “out-folding” condition represents a state that theflexible display apparatus DD is folded as illustrated in FIG. 3A. It isalso noted that “high temperature, high humidity” condition means thatthe folding test is performed under the condition of a temperature of60° C. and a relative humidity of 93%. Each of 2R, 3R, and 4R in Table 1represents a radius of curvature in the bending area of the flexibledisplay apparatus, and 2R, 3R, and 4R represent test conditions for thecases that the radii of curvature BR are respectively 2 mm, 3 mm, and 4mm in FIG. 2A or FIG. 3A.

TABLE 1 Comparative Embodiment Embodiment Test Condition Example 1 2 In-Room 4R OK OK OK folding temperature 3R NG OK OK 2R NG OK OK High 4R NGOK OK temperature, 3R NG OK OK high 2R NG OK OK humidity Out- Room 4R NGOK OK folding temperature 3R NG OK OK 2R NG NG OK High 4R NG OK OKtemperature, 3R NG OK OK high 2R NG NG OK humidity

In the test results of Table 1, “NG” represents a case that a crease hasoccurred in the phase retardation layer under the folding testconditions, and “OK” represents a case that a crease has not occurred inthe phase retardation layer under the folding test conditions. In otherwords, “NG” represents a case that a crease has occurred in the phaseretardation layer included in the polarizing member, and thus, displayquality of the flexible display apparatus deteriorates, and “OK”represents a case that the display quality of the flexible displayapparatus is satisfactory.

Referring to the test results of Table 1, it is known that Embodiment 1and Embodiment 2, in which the first adhesive member AP1 adjacent to theλ/4 phase retardation layer RC1 is composed of an adhesive layer with aglass transition temperature from 40° C. to 150° C. inclusive, showsatisfactory folding test results when compared with Comparative Examplein which the first adhesive member AP1 is a pressure sensitive adhesivelayer with a glass transition temperature from −35° C. to 0° C.inclusive. In other words, it may be confirmed that, in the case of thefirst adhesive member AP1 is composed of the adhesive layer with a glasstransition temperature from 40° C. to 150° C. inclusive, a crease doesnot occur in the phase retardation layer RC1/RC2 even under hightemperature, high humidity conditions as well as at room temperature,thereby resulting in satisfactory adhesive properties and displayquality.

It may also be confirmed that Embodiment 2, in which all of the firstadhesive member AP1 and the second adhesive member AP2 are composed ofthe adhesive layers with a glass transition temperature from 40° C. to150° C. inclusive, shows satisfactory adhesive properties and displayquality under all conditions irrespective of radius of curvature.

According to one or more exemplary embodiments, a flexible displayapparatus may obtain improved display quality by including thepolarizing member PM having the linear polarizer PP and the λ/4 phaseretardation layer RC1 that have been laminated so as to reduce externallight reflection. In one or more exemplary embodiments, display qualitymay be improved because deformation of the polarizing member PM may beminimized (or at least reduced) even when the flexible display apparatusis bent or folded, by forming the adhesive member adjacent to the λ/4phase retardation layer RC1 of the polarizing member with the adhesivelayer with a glass transition temperature from 40° C. to 150° C.inclusive. In other words, the flexible display apparatus may use thepolarizing member PM including the adhesive member that is the adhesivelayer with a glass transition temperature from 40° C. to 150° C.inclusive so that occurrence of a crease or a crack in the λ/4 phaseretardation layer RC1 included in the polarizing member PM may bereduced when the flexible display apparatus is bent or folded, and thus,change of an optical compensation value may be reduced in the bendingarea, thereby improving display quality.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the inventive concepts are notlimited to such embodiments, but rather to the broader scope of thepresented claims and various obvious modifications and equivalentarrangements.

What is claimed is:
 1. A flexible display apparatus comprising: adisplay panel; and a polarizing structure disposed on the display panel,wherein: the polarizing structure comprises: a λ/4 phase retardationlayer; a linear polarizer disposed on the λ/4 phase retardation layer;and a first adhesive structure disposed between the λ/4 phaseretardation layer and the linear polarizer; and in a plan view, an anglebetween an absorption axis or a transmission axis of the linearpolarizer and a bending axis of the flexible display apparatus is 45degrees±30 degrees.
 2. The flexible display apparatus of claim 1,wherein the polarizing structure further comprises: a λ/2 phaseretardation layer disposed between the λ/4 phase retardation layer andthe linear polarizer; and a second adhesive structure disposed betweenthe λ/2 phase retardation layer and the linear polarizer.
 3. Theflexible display apparatus of claim 2, wherein: the first adhesivestructure is disposed between the λ/4 phase retardation layer and theλ/2 phase retardation layer; and the second adhesive structure isdirectly contact with the linear polarizer.
 4. The flexible displayapparatus of claim 2, wherein a thickness of the second adhesivestructure is greater than a thickness of the first adhesive structure.5. The flexible display apparatus of claim 2, wherein a thickness of thefirst adhesive structure and a thickness of the second adhesivestructure is less than or equal to 5 μm, respectively.
 6. The flexibledisplay apparatus of claim 2, wherein: a thickness of the λ/4 phaseretardation layer and a thickness of the λ/2 phase retardation layer isgreater than or equal to 0.5 μm and less than or equal to 2 μm,respectively; and a total thickness, including the λ/4 phase retardationlayer, the first adhesive structure, the λ/2 phase retardation layer,and the second adhesive structure, is greater than or equal to 1.2 μmand less than or equal to 14 μm.
 7. The flexible display apparatus ofclaim 2, wherein a glass transition temperature of the first adhesivestructure is greater than a glass transition temperature of the secondadhesive structure.
 8. The flexible display apparatus of claim 7,wherein: the first adhesive structure is an adhesive layer having theglass transition temperature greater than or equal to 40° C. and lessthan or equal to 150° C.; and the second adhesive structure is anadhesive layer having the glass transition temperature greater than orequal to −35° C. and less than or equal to 0° C.
 9. The flexible displayapparatus of claim 7, wherein: the first adhesive structure comprises anultraviolet curable adhesive; and the second adhesive structurecomprises a pressure sensitive adhesive.
 10. The flexible displayapparatus of claim 2, wherein: the first adhesive structure is anadhesive layer having a glass transition temperature that is greaterthan or equal to 40° C. and less than or equal to 150° C.; and thesecond adhesive structure is an adhesive layer having a glass transitiontemperature that is greater than or equal to 40° C. and less than orequal to 150° C.
 11. The flexible display apparatus of claim 2, wherein,in a plan view: an angle between an absorption axis or a transmissionaxis of the linear polarizer and a first optical axis of λ/4 phaseretardation layer is 75 degrees±30 degrees; and an angle between theabsorption axis or the transmission axis and a second optical axis ofthe λ/2 phase retardation layer is 15 degrees±13 degrees.
 12. Theflexible display apparatus of claim 2, wherein, in a plan view, an anglebetween a first optical axis of the λ/4 phase retardation layer and asecond optical axis of the λ/2 phase retardation layer is 60 degrees±30degrees.